Enhanced catalytic performance of magnetic Fe3O4-MnO2 nanocomposites for the decolorization of rhodamine B, reduction of 4-nitroaniline, and sp3 C-H functionalization of 2-methylpyridines to isatins

- MnO2, Fe3O4, and Fe3O4-MnO2 nanocomposites were synthesized using leaf extract of Perilla frutescens.
- The synthetic protocol is cheap, fast, and ecofriendly.
- Owing to the synergistic effect of Fe3O4 loaded on MnO2, the synthesized nanocomposites showed strong catalytic ability.
- The magnetic Fe3O4-MnO2 nanocomposites were reused for five consecutive reactions without any significant loss of catalytic ability.

A novel biosynthesized nanocatalyst, iron oxide-loaded manganese dioxide nanocomposites (Fe3O4-MnO2 NCs), was fabricated with the aid of a Perilla frutescens leaf extract. The MnO2 is composed of numerous nanoflakes radiating from the center, which results to a flowerlike structure. A change in the flowerlike morphology of MnO2 in Fe3O4-MnO2 NCs was observed due to the distribution of Fe3O4 nanoparticles on the surface of MnO2. To check the catalytic performance of the synthesized NCs, they were utilized as a catalyst for the decolorization of rhodamine B (RhB), reduction of 4-nitroaniline (4-NA), and sp3 C-H functionalization of 2-methylpyridines to isatins for the synthesis of azaarene-substituted 3-hydroxy-2-oxindole derivatives. The Fe3O4-loaded MnO2 exhibited enhanced catalytic ability over MnO2. Moreover, the nanocomposites could be recovered by a magnetic separation technique and reused for five consecutive reactions without significant loss of catalytic ability.

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